For me personally, deficit pulls have been the single best exercise in helping me off the floor. Not only are you pulling a longer distance, but it really helped me "feel" the leg drive and make the mind muscle connection. Aside from that I also do glute-ham raises, barbell hip bridges, and cable pull through to help with hip explosion.

If you try deficit pulls, aim for about 60% of your current 1rm and start with maybe a 2" lift. Here's a vid of some of my deadlift workout from yesterday, you can see the last set of deficits I did at the start of the video.